Microencapsulated products have long been known. Generally, a microencapsulated product includes a wall material that surrounds an encapsulated core material. Innumerable uses for microencapsulated products have been described in the art, and conventional uses include, for instance, encapsulation of color developer material in carbonless copy papers. Exemplarily teachings as to microcapsules and their method of production are found, for instance, in U.S. Pat. Nos. 4,197,346; 4,725,905; 4,299,411; 5,164,126; and other patents assigned to Appleton Papers Inc., the assignee of the present application.
Microencapsulation technology is sometimes used in connection with food and medicinal products. Specifically, it is sometimes desired to mask the bitter tastes of ingredients that are orally administered. This is particularly true in the medicinal fields, where the bitter taste of the active agent can contribute to patient non-compliance in taking medicines. In accordance with some conventional techniques, bitter medicinal ingredients are microencapsulated within a capsule wall. The capsule wall is intended to block the diffusion of the material out of the microcapsules.
In this conventional approach, the microcapsule walls may lose their barrier properties when placed into contact with moisture, such as that present in the oral cavity. This is especially true when the wall is composed of gelatin, a common microcapsule wall material. If the capsule core is composed of a small molecule with a low viscosity, diffusion out of the capsule core and into the wall may occur, with equilibrium becoming established between the capsule core and the matrix. For some encapsulated payload ingredients, the taste threshold can be as low as parts-per-million, or even parts-per-billion in some cases. This threshold is detectable in the wall material, thereby making it difficult to mask taste effectively. This is especially true from small molecular bioactives in a liquid state that are intended for oral administration.